The present invention relates to a semiconductor device and, more particularly, to a method of forming contact plugs of a semiconductor device, which can simplify the contact plug formation process and reduce the prime cost.
As devices are miniaturized below 60 nm, a problem arises with some of the photomask processes. When forming the drain contact plug of a cell region and the contact plug for a high voltage device of a peri (peripheral) region, these photomask processes cannot be performed at the same time.
This is because a drain contact hole and a contact hole for a high voltage device have different shapes and sizes. If a mask formation process is performed on the basis of any one region, mask patterns formed on the other region deviate from the specs, making it difficult to form the drain contact hole and the contact hole for a high voltage device with a desired size. The drain contact hole is gap-filled with a polysilicon layer and the contact hole for a high voltage device is gap-filled with a tungsten (W) layer. Therefore, the process of forming the drain contact plug and the process of forming the contact plug for a high voltage device cannot be performed at the same time.
As described above, the process of forming the drain contact plug and the process of forming the contact plug for a high voltage device are not performed at the same time, but separately carried out due to the mask formation process problem and a difference in materials for gap-filling the drain contact hole and the contact hole for a high voltage device. At this time, since the photomask process is performed under the ArF condition, subsequent processes are added. Accordingly, manufacturing costs for forming mask patterns are increased due to the added subsequent processes.